The present invention relates in general to cleaning of a pressure roller for an electrostatographic reproduction apparatus fusing assembly, and more particularly to a particularly shaped blade for cleaning the pressure roller of a fusing assembly.
In typical commercial electrostatographic reproduction apparatus (copier/duplicators, printers, or the like), a latent image charge pattern is formed on a uniformly charged charge-retentive or photoconductive member having dielectric characteristics (hereinafter referred to as the dielectric member). Pigmented marking particles are attracted to the latent image charge pattern to develop such image on the dielectric member. A receiver member is then brought into contact with the dielectric member, and an electric field applied to transfer the marking particle developed image to the receiver member from the dielectric member. After transfer, the receiver member bearing the transferred image is transported away from the dielectric member, and the image is fixed (fused) to the receiver member by heat and pressure to form a permanent reproduction thereon.
The fixing process is typically carried out by passing a receiver member, bearing a marking particle developed image, through a fusing assembly including a nip roller pair. At least one of the rollers of the nip roller pair is heated to cause the marking particles to soften and become tacky. The rollers are urged into a predetermined pressure relation so as to force the softened marking particles to the receiver member. For example, for a paper receiver member, the marking particles are forced into the interstices of the paper fibers and become imbibed therein so that on cooling the image is fixed (fused) to the paper receiver member.
In the fusing assembly of the above described type, it has been found that the marking particles generally have an affinity for the nip rollers. Since the particles would thus tend to stick to the rollers and cause unacceptable artifacts in reproductions, a release liquid is applied to the rollers to inhibit the ability of the particles to stick to the rollers, and encourage their adherence to the receiver member. For example, a typical release liquid is silicone oil. The release liquid tends to accumulate on the rollers towards the outboard ends. This is due to the fact that release liquid is provided so as to cover the roller surface over the area contacted by the widest receiver member to be handled by the fusing assembly. Since receiver members tend to absorb release liquid and remove it from the rollers, for receiver members of less width than the maximum, liquid is left on the rollers adjacent to the outboard ends (i.e., the area not contacted by the narrower receiver members). This excess release liquid then becomes a contaminant within the reproduction apparatus.
The harsh environment of the fusing assembly (i.e., the combination of the release liquid along with the heat and pressure) has been found to cause undue build-up on the rollers of residue such as paper dust or marking particles for example. One mechanism for preventing residue build-up on the fixing assembly rollers is to provide a cleaning blade in association with a roller. The engagement of the cleaning with the roller causes the blade to effectively scrape the surface of the associated roller and chisel off contaminates such as paper dust and/or marking particle residue. However the blade also has a tendency to skive off the excess release liquid. As a result, the liquid tends to accumulate along the blade as puddles which may cause deterioration of the roller, and will eventually roll off the ends of the blade into the reproduction apparatus and contaminate other parts of the apparatus. U.S. Pat. No. 5,493,375 (issued Feb. 20, 1996, in the name of Moser) describes a blade constructed to urge release liquid toward the outboard end of a fusing assembly roller and collect such liquid. This of course, necessitates additional structural elements which increase the complexity and expense of the reproduction apparatus.